1. Field of the Invention
The present invention relates to a device for supplying a developing solution to the circumferential surface of a latent-image carrier in a wet-type electrophotograhic copying machine.
2. Discussion of the Background
Wet-type electrophotography is known in which an elestrostatic image carried on a latent-image carrier such as a photosenstive drum is visualized by a developing solution supplied to the circumferential surface of the latent-image carrier. One known arrangement for supplying the developing solution to the latent-image carrier is disclosed in Japanese Laid-Open Patent Publication No. 57-20056.
In the disclosed supplying device, the developing solution is ejected from a supply nozzle onto a guide plate from which it flows down to the latent-image carrier. The developing solution then flows down the circumferential surface of the latent-image carrier to form a solution pool between the latent-image carrier and a developing roller disposed adjacent thereto.
Another conventional developing solution supplying device has a supply nozzle opening above a region where a latent-image carrier and a developing roller are disposed in confronting relation to each other. The developing solution ejected from the supply nozzle directly forms a solution pool between the latent-image carrier and the developing roller.
In the above prior solution supplying arrangements, the developing solution is supplied from the solution pool through a small gap between the latent-image carrier and the developing roller uniformly onto the circumferential surface of the latent-image carrier.
When the electrophotographic system starts to operate, air bubbles tend to be trapped in the developing solution discharged from the nozzle due to air present in the supply tube. Air bubbles are also liable to be produced in the developing solution when it is deteriorated. In addition, since the developing solution is forcibly ejected from the nozzle and impinges upon the guide plate, the solution pool between the latent-image carrier and the developing roller contains many air bubbles, which lower the developing ability of the developing solution and degrade the quality of developed images.
The amount of the pooled developing solution is greater in the vicinity of the nozzle and becomes smaller in a direction away from the nozzle. If the developing solution were supplied in a larger quantity from the nozzle, then the pump for feeding the developing solution would be heated to cause a temperature rise of the developing solution, and an increased amount of developing solution would be directly applied to a localized surface portion of the latent-image carrier, with the result that no uniform images would be produced. Stated otherwise, surface portions of the latent-image carrier which are close to and remote from the nozzle would be supplied with different amounts of developing solution, resulting in image density irregularities.